#21 Browser's gauge cannot change place

[George P]

Browser's gauge position cannot be controlled, it is always displayed on top.

[Pashalis Padeleris]

Added a new method on the PageListener interface: pageLoadProgress(). This method allows the PageListener implementation to know about the progress of the operation. The gauge is now managed by the default PageListener (the browser instance). If the programmer provides another PageListener implementation it can be used to create and update its own progress bar.